HEP­par­ti­cles is a set of macros for type­set­ting high en­ergy
par­ti­cle names, to meet the fol­low­ing cri­te­ria:

1. The main par­ti­cle name is a Ro­man or Greek sym­bol, to be
type­set in up­right font in nor­mal con­texts.

2. Ad­di­tion­ally a su­per­script and/or sub­script may fol­low the
main sym­bol.

3. Par­ti­cle res­o­nances may also have a res­o­nance spec­i­fier
which is type­set in paren­the­ses fol­low­ing the main sym­bol. In
gen­eral the paren­the­ses may also be fol­lowed by sub- and
su­per­scripts.

4. The par­ti­cle names are ex­pected to be used both in and out
of math­e­mat­i­cal con­texts.

5. If the sur­round­ing text is bold or italic then the par­ti­cle
name should adapt to that con­text as best as pos­si­ble (this may
not be pos­si­ble for Greek sym­bols).

A con­se­quence of point 5 is that the well-known prob­lems with
bold­ness of par­ti­cle names in sec­tion ti­tles, head­ers and
ta­bles of con­tents au­to­mat­i­cally dis­ap­pear if these macros are
used.